I never made it through to the end without using cheats as a kid. Having played through it for Twitch recently, I understand why. This game is brutally hard at times. Enemies can drain your health with one burst of their smg, and you can't effectively dodge because of clunky PS1 collision detection. It's unfortunate, as this game's high points are very high. The catacomb level, Morocco, and the entire Crete sections are incredible. Being able to play as a woman French resistance fighter is a nice touch, too. On top of that, this game has some of the best graphics the PS1 ever had. This could have been a better game than the first one, but its relentless, unfair difficulty and poor collision detection hold it back. This game is worth at least a look, but as far as first-person shooters from 2000 go, you'd be better off playing Perfect Dark, preferably the remake of it they did for the Xbox consoles, though the Nintendo 64 version works just fine, too.

This is the second entry in my quest to play all of the mainline Medal of Honor games.
So, to get a few things out of the way first:
This game would be a 4/5 if it ended after the fifth chapter.
Normal, sane people would use an emulator to avoid the severe performance issues plaguing this game. However, I am not a normal or sane person, so I played this all the way through on original hardware because I hate myself.
That being said, this game had a lot of potential but was dragged down by several nagging issues. I'm not one of those people who plays through the first few levels of a game to wax nostalgic about playing the easy levels as a kid, then gives a game five stars. If you read my Medal of Honor 1999 review, you'd know I'm tough, but fair in my analysis. That game was a fairly flawed, but very good game with some issues dragging it down towards the end. It had a lot of heart and soul poured into it that made it a fun experience, despite being a first person shooter on the PlayStation 1. Its sequel, Medal of Honor: Underground, on paper, should be the better game. It has better graphics, better lighting, a better soundtrack, a more interesting story that has you playing as Manon, a female French resistance soldier who sabotages the Nazi war machine on behalf of the OSS, the precursor to the CIA. The problem is, it's not.
To start, the first five chapters have some fairly low points but as a whole, I would say are better than the first game by a long shot. Especially the missions in Africa. They almost feel like a prototypical version of Return to Castle Wolfenstein, a game that released about a year after this one, with their more supernatural and medieval elements.
The guns you are given are inferior to those in the first game. You get no good medium-range rifles like the M1 garand when playing as Manon. You are mostly stuck with submachine guns, pistols, a shotgun, and a sniper rifle. The sniper rifle would be great, were it not for the abysmal draw distance. A rifle without a scope, such as the M1 garand, would be a much better offering. The BAR was an absolute godsend in the final missions of the first game, but you are not given a weapon like that in this game for the more difficult Manon missions. I understand why you aren't given American weapons for reasons of historical authenticity, but still, some of the weapons Jimmy Patterson had in the first game would've been nice. Especially because you are given these missions by the OSS.
The story, just like the one in the first game, is your standard World War II shooter fare. You kill Nazis. Sometimes you do it in castles, sometimes you do it in a labyrinth, and sometimes you do it in the streets of Paris. This one has more interesting set dressing, like supernatural elements, but other than that it's your standard game about the French resistance.
The graphics are great, but the bad lighting returns from the first game. This predates the time when most games had a brightness slider, so if you want to see, then you'll have to turn up the brightness on your TV. The graphics are more varied, but the levels are more complex, so it evens out the complexity of the levels.
The levels themselves start off really fun and engaging, and the game feels a little smoother to play. That is, until the last few levels. The game always has an issue with performance, but there are so many enemies in the final two chapters with Manon that the frame rate drops into the single digits and you could fry bacon on your Playstation. You'd think they'd tone down the difficulty and number of enemies because performance drops like that are a really bad look for developers, but they didn't.
The enemies have more advanced and more obnoxious AI as well. They take cover, they duck, etc. The ducking is annoying because, even with bullet magnetism turned on, you have to aim like a foot lower than the actual soldier because the crosshair is askew. This is a problem in many situations, and with multiple weapons. The enemies also have this annoying habit of zipping around like meth heads (which, to be fair, is historically accurate) and being impossible to shoot. This is especially bad with the tankier submachine gunners, who will zip right up to you and mag dump right into you without you even noticing what happened. The game is plagued with these submachine gunners in the later chapters. It's even worse knowing that this is from an era where developers didn't respect your time and sanity, so you have to restart the entire mission when you die. These enemies also slow the game down much more than regular enemies, so you end up having to memorize their positions and anticipating them. You can't pick them off from a distance either, because they take cover behind impenetrable walls and don't aggro until you're right in their faces. They also love to corner camp so much that they'd make your average MW2 2009 player call BS. The Panzerschreck enemies also make a return, but they're not as numerous as they were in the first game. They'll still completely ruin your day if you're not careful.
Over the course of this entire game, I had a lot of fun and would highly recommend playing this for the first five chapters. The sixth and seventh chapter have genuinely unfair design that tanks the performance. I'm no stranger to hard games, but the last two chapters make me say that this is a bad game as a whole. It makes me wonder if everyone except a scant few played a different game altogether, because no one on the internet, not even Gmanlives, talks about the horrendous final levels.
There's also Panzerknacker Unleashed, the joke epilogue where you play as previous protagonist Jimmy Patterson. These missions are also horrendously difficult, with the developers continuing to indulge in their SMG fetish. The first level has you don your ATF hat and shoot a bunch of dogs, some of which wield our favorite firearm. You're just given a shotgun and pistol for this one. The second level has you fighting exploding zombies with SMGs and knights. These zombies, like the soldiers in the base game, have insane reflex time and aim. The mission is straight up unfair, like the last one. Luckily you get a BAR, which will carry you through the whole thing. The third has you killing nutcrackers. Enough said.